The present invention relates to a resin degassing and, in particular, to a method and system for using ultrasonic energy to degas resins.
Gas and air bubbles can become trapped in a multi-part resin system as a result of typical mixing processes. The air bubbles are formed from the mixing or “folding” operation required to evenly disperse the multiple parts of the resin system. Use of a resin with entrapped air or gas bubbles in a composite laminate creates a source of defects that can link-up or grow to create local and ultimately global disbonding or delaminating.
Large-scale, continuous fiber reinforced composite components, such as wind turbine blades, or other large composite structures, are typically fabricated by a hand lay-up method. The hand lay-up method typically includes positioning a continuous fiber tape or fabric into a mold and pouring a liquid resin onto the fiber tape or fabric. The blend is then rolled manually to work out any air bubbles and to fully distribute the resin along and within the fiber network. This is followed by a cure process that is typically performed at room temperature for large components. The manipulation of the resin to remove air bubbles and to distribute the resin along and within the fiber network may result in damage to the fibers making up the composite with the consequence being a reduction in strength and stiffness of the component. This method suffers from the drawback that the processing method is labor intensive and suffers from high costs. Alternative methods, such as resin film infusion (RFI), are desirable techniques due to the decreased labor costs related to performing RFI and the reproducible parts that may be achieved. The curing typically takes place at elevated temperatures in an autoclave and the cure is done in a vacuum bag under high pressure (typically 100-200 psi) in order to make the resin flow and remove entrapped air and condensable gases. However, large scale components such as wind turbine blades make autoclave curing cost prohibitive due to the size of autoclave required.